Core binder

Patented Sept 24, 1940

2,215,825

UNITED STATES PATENT OFFICE 2,215,825

CORE BINDER ^Bro0klvn^Fv^^iUac'L^a«^d ,^Bur«ess P. Wallace, Brooklyn, N. Y.; said Benjamin F. Wallace assignor to Matilda Wallace and said Burgess P Wallace, both of Brooklyn, N. Y., jointly

No Drawing. Application March 16,1938 Serial No. 196,151

Claims. (Cl. 22—188) invention relates to sand cores for use casting of metals and has for its parobjects the expeditious and economical

This in the ticular production of such cores as well as^he^mini5 mizmg of the evolution of acrid fumes during such production. Further objects of the invention comprise the production of a core having tn fnsw¹ S?^nd °^{Γ unbaked} strength adequate a h.^“^e to maintain its shape during the “θ baking operation and which core when baked is sufficiently strong to be unaffcted by the action ?L^thX?°^Wlni\^{metaI during a casting} operation

J^e; °an ^be readily disintegrated and rein from the completed casting

Still other objects of the invention comprise the utilization m the production of such cores ^a ”^οη.·°foagmous, highly water-soluble base ingredient which comprises either a molasses such for example as black strap molasses, an uncrystalhzable sugar, such as glucose and dexMrnfn; ^a.^sfcarch °^{r dexfc}rine, a sulphite pulp waste Jtouor. i. e. goulac or glutrin, and like products which readily reduce Fehling’s solution and 25 ^art°i ^themselves highly water-soluble.

ii'ther objects of the invention will hereinafter appear.

At the present time in the production of foundry cores it is customary to employ a core oil ^{38 011 is essentiall}y watersoluble. This oil binder not only requires the employment of a high temperature for the bak°^f ?^re:· ^{but during the baking} operation yields a voluminous amount of acrid smoke or fumes. Such binders are also relatively expensive and they do not possess the inherent property of causing the sand particles to cohere to a?d htodTr ^dt^UrI^ ^{the initlaI mlXing of the sand aPd bmder} together and prior to the baking of the formed core.

In carrying out our invention, we preferablv proceed as follows: ^y nJJo f^a£i^S ®^ulphate °f ammonia and 1100 ^{pa of black} strap molasses are first dissolved as IS · ^{parts of} water while constantly agitating the mixture. Then 120 parts of a water-soluble ^g«^CerP’-ottrio-aold resin, prepared as hereinafter described, is added and the mixture is thoroughly agitated until the resin is completely dissolved therein. ^y

Due to the tendency of the molasses and the resin-like element of the aforesaid mixture to migrate to the surface of the core during the baking operation, an emulsion consisting of 265 55 ^pafJ^s °f ^Chlnese wood ⁰¹¹ (tuns oil) and 15 parts of karaya gum dissolved in 140 parts of ' water is then added with constant stirring to the foregoing mixture. Then to the resultant mass a preservative, preferably about 15 parts stirring unti^h¹’ ^{iS added aI}®° ^{wlth constant}thereto ^{W th Same 1S comp!etel}V dissolved δ

I°^regoing glycerol-citric-acid resin is preHlSi Pa«S or gtycerta M citric acid and heating to a temperature of anriZ™? ²²°t;^C· ^{for a sufflcient} time to pl?- 10 J ^a*^lyJ°“^dense the resin and effect the evaporation of the water of condensation formed during n^{f desired}’ however, to lieu of adding the partially polymerized resin to the molasses base as aforesaid, the same quantities of ¹⁶glycerine and citric acid may be incorporated wto^Ch ^y_f^lnt0 λ¹¹·^{6 mixture and} the desired resin Xatnn “ ^{thereta during the bakin}^ upci aulUH.

°^^ei^{to produce a core} employing the fore- ²⁰going binder, approximately 30 to 60 parts of green sand are mixed with one part of our improved binder and a core of the desired shape ^m°^{lded therefrom}· Then the same is baked in an oven at a temperature preferably ²⁵betw^{een 18}°_{: c}. _{t0 300}, _{c such bak}^{p a}“^ytion continuing preferably until the core is thoroughly baked throughout. The resultant core is highly water-insoluble and a specimen thereof if submerged in water for 24 hours will show no ³⁰fr™tb^aMnF °^{f th},^{e Water and>} when removed from the water and allowed to dry, will be found to be unaffected by such submersion.

The ammonium sulphate during the baking of the core reacts with the molasses to form a black resin-like substance or magma which is essentially substantially water-insoluble and, due to the partial migration of the molasses, and the glycerol-citric-acid resin during the baking opfo?m?ri’w^{e SheU} °^{f the COre bec}°mes transformed into an unusually tough and water-insoluble shell which is entirely resistant to and unaffected by the action of the molten metal. The function of the drying oil and gum emulsion is to bind together the sand particles and thereby reinforce the inner portion of the core which would otherwise be unduly weakened by such partial migration of the molasses and glycerolcitnc-acid resin, prior to the conversion of the same into an insoluble condition, to the outer ⁵⁰layer of the core.

While we preferably employ ammonium sulphate as the agent for rendering insoluble the molasses or like water-soluble, reducible base, other compounds having similar properties, such as for ⁵⁵

2,215,825 example sulphuric acid, ammonium alum, ammonium phosphate, chloride or persulphate, and which compounds on heating produce an acidreacting substance, may be substituted therefor.

Also in lieu of a glycerol-citric-acid resin, a mixture of either tartaric, malic, fumaric, succinic or like fruit acids with glycerine may be substituted, the same being either introduced into the molasses or like water-soluble base with10 out being previously heated or being heated prior to such introduction to partially condense the same without objectionally affecting the solubility thereof.

Such compounds as sodium borate, caustic 15 soda and like substances which have an alkaline reaction are entirely unsuited for use with molasses or like water-soluble base in the production of our improved binder.

While we prefer tung oil, owing to its charac20 teristic property of polymerizing to a jelly-like mass when heated, other drying oils, such for example as linseed, soya bean or perilla may be used in lieu thereof.

The karaya gum, which may be substituted by 25 other water-soluble gums, as for example gum arabic and gum tragacanth, or by gelatin, serves to facilitate the formation of a better and more permanent emulsion than is obtainable when water and a drying oil are emulsified alone. The θ® function of the aqueous oil-gum emulsion, in addition to that above described, is to render the baked core even more water-insoluble than if the same were omitted from the core binder.

In foundry operations, it is often customary to store sand cores after the same are baked for considerable periods before use for metal casting purposes and while so stored the cores are exposed to the prevailing atmospheric moisture. Also it is customary to insert the baked cores 40 into position in a mold wherein such cores are frequently allowed to remain overnight in contact with the moist molding sand. Accordingly, the characteristic of being water-insoluble and thereby being unaffected by atmospheric moisture 45 or moist sand is of no inconsiderable importance in the case of a baked sand core for use in such operations.

Preferably we employ an ammonium salt of a poly-basic, difficultly volatile, mineral acid, as 50 the agent for converting to an insoluble magma the molasses, or like base, such as hereinbefore defined.

Various changes in proportions and the details of manufacture from that herein described 55 may be made without departing from the spirit of our invention as embraced within the scope of the appended claims.